This invention relates to a photoreceptor useful in electrophotography. More particularly, this invention relates to an electrophotographic photoreceptor comprising in sequence a conductive base layer and at least one photosensitive layer applied to the conductive base layer, the photosensitive layer comprising at least one organic material and 0.01-3 weight percent of a titanate coupling agent.
Inorganic materials such as Se, CdS and ZnO have conventionally been employed as photoconductive materials in electrophotographic photoreceptors. However, it has been found that these materials do not always have the properties necessary to function properly in a photoreceptor. As a result, organic photoconductive materials have been recently employed in photoreceptors. When organic materials are employed, the photoreceptor is generally advantageous in terms of plasticity, thermal stability, film formation properties, light transmittance and reduced manufacturing costs. However, such materials are generally disadvantageous in terms of dark resistance and photosensitivity. Accordingly, photoreceptor compositions employing organic materials generally comprise a laminate of layers serving different functions: for example, a layer mainly contributing to charge generation when illuminated, and a layer mainly contributing to maintenance of surface charge in the dark and transportation of charges at the time of illumination. Different organic materials suitable for each of these functions are typically selected, thereby improving the electrophotographic properties of the photoreceptor as a whole.
Although methods such as vacuum deposition have been proposed for the manufacturing of photoreceptors employing an organic material or materials, a coating method of applying the organic material generally predominates due to its cost advantages. In the coating method, a coating liquid is first prepared by dispersing or dissolving a charge-generating material or a charge-transporting material in a solvent together with an appropriate binder material. The coating liquid is thereafter applied to a base layer by a dipping method or the like to provide the above-described layer or layers of the photoreceptor composition. However, the coating method is disadvantageous in that it is apt to produce defects in the coating film surface. Such defects are characterized herein by the specific terms "sag" and "orange peel". As is well known to those skilled in the art, such defects detract from the stability, external appearance, and surface quality of the photoreceptor.
Accordingly, it is the object of this invention to provide an electrophotographic photoreceptor composition comprising at least one photosensitive layer which comprises at least one organic material, the photoreceptor composition having good external appearance, a surface free from coating film defects such as "sag" and "orange peel", excellent electrophotographic properties, and the capability of being produced in a stable form at low cost.